Modes of Inheritance

Two copies for each trait exist in the genome. An animal derives one of each of thesecopies from the father and one from the mother. A recessive allele is overwritten by it'sdominant counterpart. Therefore, autosomal recessive inherited diseases only affectanimals which received two mutated alleles. Father and mother of the affected animalhave to carry the recessive allele, but could be healthy themselves.Three possible genotypes exist:1. Genotype N/N (homozygous healthy): This animal does not inherit the mutation andcontracts the disease with very low probability. The animal will never pass a mutatedallele to it's offspring.2. Genotype N/mut (heterozygous carrier): This animal posses one copy of the mutatedallele with a very low probability to contract the disease. The offspring of the carrierinherit the mutated allele with 50% probability. Therefore, breeding should only takeplace with homozygous healthy animals.3. Genotype mut/mut (homozygous affected): Carrying two mutated copies of the allele,this animal will most probably exhibit the disease. Additionally, 100% of it's offspringinherit the mutated allele. Only breeding to a mutation free animal could be tolerated.With 50% probability carrier animals inherit the mutated allele to their offspring. Breedingtwo carriers results in 25% of the offspring being affected by the disease.In healthy populations, carrier animals enlarge the gene pool and should not be excludedfrom breeding categorical. Never the less, breeding of carriers with other carriers or evenaffected animals should strictly be avoided.

Two copies for each trait exist in the genome. An animal derives one of each of thesecopies from the father and one from the mother. A dominant allele overwrites it's recessivecounterpart. Therefore, autosomal dominant inherited diseases affect animals whichreceived one mutated allele. Either father or mother of the affected animal have to carrythe mutated allele and are affected by the disease themselves.Three possible genotypes exist:1. Genotype n/n (homozygous healthy): This animal does not inherit the mutation andcontract the disease with very low probability. The animal will never pass a mutatedallele to it's offspring.2. Genotype n/Mut (heterozygous affected): This animal posses one copy of the mutatedallele with an increased probability to contract the disease. The offspring of the carrierinherit the mutated allele with 50% probability.3. Genotype Mut/Mut (homozygous affected): Carrying two mutated copies of the allele,this animal will most probably exhibit the disease or die at very young age. Additionally,100% of it's offspring inherit the mutated allele. As both parents have to be affectedanimals, this genotype is very rare.Autosomal dominant traits often increase the risk to contract the inherited disease. Thosechanges in probability for the disease to occur are called variable penetrance of themutation. Therefore, carriers of the mutation and affected animals do not exhibit thedisease by 100%.As in some diseases symptoms just develop in old age, the necessity arises to test theanimal for the mutation before breeding.

Two copies for each trait exist in the genome. For gonosomal coupled traits, an animalderives an X- or Y-chromosome from the father and one of two X-chromosomes from it'smother. The mutated allele resides on the X-chromosome only.Five possible genotypes exist:Female animals:1. Genotype xN/xN (homozygous healthy female): This animal does not inherit themutation and contracts the disease with very low probability. The animal will never passa mutated allele to it's offspring.2. Genotype xN/xmut (heterozygous carrier female): This animal posses one copy of themutated allele with a very low probability to contract the disease. The offspring of thecarrier inherits the mutated allele with 50% probability.3. Genotype mut/mut (homozygous affected female): Carrying two mutated copies of theallele, this animal will most probably exhibit the disease. Additionally, 100% of it'soffspring inherit the mutated allele.Male animals:4. Genotype xN/y (healthy male): This animal does not inherit the mutation and contractsthe disease with very low probability. The animal will never pass a mutated allele to it'soffspring.5. Genotype xmut/y (affected male): Carrying one mutated copie of the allele on it's onlyX-chromosome, this animal will most probably exhibit the disease. Additionally, 100%of it's female offspring inherit the mutated allele.For an x-chromosomal recessive trait, male carriers of the mutated allele are affected bythe disease and inherit the mutation to 100% of their female offspring. Their sons can onlyobtain the mutated allele from the mothers side.The inheritance for female animals follows an autosomal recessive trait. Female carriersdo not exhibit symptoms, but pass the mutation with 50% probability to all of theiroffspring, which results in 50% of the males being directly affected.

The following factors describe the difference between the presence of a mutation and theoccurance of clinical symptoms of the corresponding disease:

PenetranceThe term penetrance indicates the proportion of individuals carrying a particular variant(allele) of a gene, that actually express the associated phenotype. There is a distinctionbetween the complete penetrance ( if the allele is present, the associated phenotype isgenerally expressed) and the incomplete or reduced pentetrance (some individuals will notexpress the associated phenotype even though they carry the allele).

ExpressivityThe term expressivity describes the extent of the expression of a genetic caused trait at thesingle individual.

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LABOKLIN has many years of experience with the implementation and development of genetic tests, particularly in the areas of genetic disorders, colour analysis, DNA profiles, ancestry and sex determination in birds. Our high quality standard is characterised particularly by the fact that all the results of our genetic studies are controlled in a second independent test run before they are shipped.